A polyp is generally a growth that projects from a membrane in the body. The shape of a polyp is often described as pedunculated or sessile. Pedunculated polyps grow on stalks, while sessile polyps may have broad bases and a flat appearance. Often, polyps form on mucous membranes such as those lining the colon, bladder, uterus, cervix, vocal cords, and/or nasal passage and protrude into a body cavity. Polyps are problematic in that they may block a passage, and/or may become cancerous. Generally, the larger the polyp, the more likely it is to become cancerous.
Endoscopic polypectomy procedures are effective in removing pedunculated polyps; however, sessile polyps are often problematic. For example, because of their flat, diffuse appearance, sessile polyps may be difficult to snare and excise with electrocautery. To facilitate excision of some polyps, saline may be injected into the submucosa of a polyp to create an artificial cushion that raises the polyp. However, saline has a short residence time in the submucosa: it usually clears within 4 to 5 minutes after injection.
In addition, large polyps are often difficult to remove as a whole, so they are often excised in piecemeal fashion. After the first excision of polyp tissue, injected solution may escape from the submucosa causing the polyp to collapse, thus making it difficult to remove the remaining portions of the polyp. Although saline may be re-injected, it escapes quickly and is not very effective in raising the remaining portions of the polyp.
Attempts to improve submucosa residence time of injection solutions have been reported. For example, solutions of glycerin, dextrose, hyaluronic acid, and hydroxpropyl cellulose have been reported as injection solutions. In some cases, hyaluronic acid may be effective. The average residence time of hyaluronic acid solutions in porcine esophagus is reportedly 21.5 minutes. However, these solutions may still leak out of the submucosal layer once the cushion is breached during the endoscopic dissection or polypectomy.
Means for introducing injection solutions into a polyp include endoscopic methods which may, in embodiments, include the use of catheters and/or cannulas. As is within the purview of those skilled in the art, cannulas may include tubular, flexible, surgical instruments for withdrawing fluids from (or introducing fluids into) a cavity of the body. Cannulas may have a single lumen or may have multiple lumens; multi-lumen cannulas, including dual lumen cannulas, are also within the purview of those skilled in the art.
Various configurations for multi-lumen catheters and/or cannulas are also known. For example, U.S. Pat. No. 4,385,631 discloses a hemodialysis catheter having two circular lumens arranged side by side. U.S. Pat. No. 4,099,528 discloses a coaxial double lumen cannula and U.S. Pat. No. 4,493,696 describes a coaxial double lumen catheter.
There remains room for improvement in compositions and methods for performing endoscopic polypectomy procedures, as well as instruments suitable for introducing polymeric materials into the body.